The preferred embodiment relates to a method and an apparatus for generating a developer mixture in a developer station for an electrographic printing or copying device. Such devices operate in accordance with the electrographic principle according to which image information is generated on an intermediate carrier pixel-by-pixel by, for example, electrical, magnetic and/or optical signals in the form of an electric charge or magnetic fields, and the intermediate carrier is inked with toner pixel-by-pixel. The inking is done in particular with a two-component developer mixture and can be achieved with the aid of a magnetic brush generated with magnets or according to the so-called “toner jump” principle. The developer mixture comprises charged and/or magnetized particles, so-called carrier particles, and toner. The toner image can then be transfer-printed onto a recording medium, in particular onto paper.
A printing device operating in accordance with the electrophotographic principle according to which the image information is generated on a photoconductive layer by means of light is known from DE-C1-19540138. From WO-A1-98/27472, a developer station operating according to the “toner jump” method is known.
From U.S. Pat. No. 4,511,639, a method for recovering a developer mixture in an electrophotographic printing system is known. Although the lifetime of the developer mixture can be increased by such methods, it is necessary from time to time to completely replace the mixture in order to guarantee a high quality of the printed images.
From EP-B1-1 016 935, a printing system is known in which aggregates such as a developer station have an electronic memory for storing operating values.
From WO-A2-02/067060, a method for the continuous replacement of carrier particles in a developer station is known.
From WO-A1-98/39691, an electrophotographic printing device is known which comprises several developer stations. WO-A1-98/27466 shows an equivalent device.
From U.S. Pat. No. 5,592,270, a method for filling an electrophotographic developer station with carrier particles and toner is known, wherein the toner inflow and the carrier particles inflow can each be separately controlled.
From EP-B1-1 016 935, a printing device is known, in which various aggregates are provided with an electronic memory element in which aggregate-specific values can be permanently stored.
The afore-mentioned publications are herewith incorporated by reference into the present application.
In large electrographic printing devices having high printing rates of some dozens of pages DIN A4 per minute up to more than 1000 pages DIN A4 per minute, relatively large amounts of developer mixtures have to be provided. In such devices, this provision is relatively time-consuming if the toner and the ferromagnetic carrier particles are only mixed when they are already in the developer station and, in addition have to be activated, i.e. have to be continuously mixed with one another over a certain minimum amount of time in order to build up a triboelectric potential in the developer mixture. This time-consumption is particularly disadvantageous insofar as during this time the printing machine is out of service.